Thyristors are bi-stable elements, consisting of two interacting PNP and NPN bipolar transistors configured in a PNPN arrangement, that can be triggered from an off-state into a very low ohmic on-state. Conventionally, a positive current is applied to the base of the NPN transistor in order to trigger the device.
For some applications, particularly those in which the thyristor operates at high positive voltages, it is desirable to be able to trigger the thyristor by using a negative current. It is known to trigger a thyristor by providing a negative current to the base of the PNP transistor. It is also known to trigger a thyristor by providing a negative current to the emitter of the NPN transistor.
Devices configured for such known negative current triggering methods may suffer from one or more disadvantages such as non-stable breakdown voltages which vary across typical manufacturing process spreads, excessive trigger currents, and increased voltage drop resulting in increased dissipation in the on state.